(AP) -- The Iraqi air force and the U.S.-led coalition have stepped up a campaign of airstrikes on the Islamic State group-held town of Hawija yesterday ahead of a planned ground assault there, according to Iraq's minister of defense.

Also yesterday, the secretary general of the Arab League visited Baghdad to encourage political dialogue with Irbil as Iraq's Kurdish region pushes forward with plans to hold a referendum on independence Sept. 25.

Despite ongoing military operations to clear out the last pockets of territory held by IS, the looming referendum has increased tensions between the central government and the Kurdish region.

"There are large operations underway ahead of the liberation of Hawija and surrounding areas," Iraqi Defense Minister Erfan al-Hayali told The Associated Press, explaining that his forces were working closely with Iraqi Kurdish forces known as the Peshmerga as well as the coalition.

During the operation to retake Iraq's second-largest city, Mosul, Iraq's military coordinated attacks with the Kurdish Peshmerga forces. After a grueling nine-month fight Mosul was declared liberated in July.

Last month, the Iraqi military command overseeing the IS fight declared victory in Tal Afar and announced Hawija would be the next battle against the extremists.

The stepped-up coalition strikes are targeting IS territory in western Anbar as well as Hawija, said U.S. Army Colonel Ryan Dillon, coalition spokesman.

The United Nations said the operation to retake Tal Afar forced some 20,000 people to flee, according to counts by Iraqi authorities. When the fight for Hawija begins, the U.N. estimates some 60,000 people will be impacted.